CARDIOVASCULAR JOURNAL OF AFRICA • Volume 34, No 1, January–April 2023 14 AFRICA provides an instantaneous peak flow rate whereas regurgitation is of a dynamic nature,24 with duration of regurgitation,25 and machine settings can vary.26 These limitations also apply to the PISA-derived estimated EROA and RVol, although these variables are more susceptible to errors, which are squared in the formulae.6 Cawley et al. found in a prospective study, poor reproducibility of RVol assessment by the PISA method and reported superiority of CMR with low interobserver variability.21 With regard to the different TTE methods of quantification, our study showed that PISA was not feasible in 62% of patients. These rates were above those found in recent research.27 These disparities can be explained by the method of selection of our patients; indeed, most of them had poor echogenicity and inconclusive quantification of AR, as reported by the operators. In patients with a possible TTE quantification, CMR allowed a re-grading of AR in 36% of patients: 10% of patients frommild AR with TTE to moderate AR with CMR, 8% from moderate AR with TTE to mild AR with CMR, 2% from moderate AR with TTE to severe AR with CMR, and 16% from severe AR with TTE to moderate AR with CMR. Our study found that the highest rate of re-grading was achieved in severe AR with TTE, which was finally classified as moderate AR on CMR. This finding was also made in a recent study that found an overestimation of severe AR using TTE. MRI re-graded severe AR on TTE in 34% of cases.27 Despite low proportions of severe AR, Gelfand et al. showed that more than half of the cases were re-graded by CMR.14 The American Society of Echocardiography/Society for Cardiovascular Magnetic Resonance recommends thresholds for AR grading with CMR by AR volume or AR fraction equivalent to TTE cut-off values.6 This can cause a mismatch in AR grade by TTE and CMR. Considering the clinical importance of this differentiation, CMR-specific cut-off values appear better suited to provide reasonable overlap with TTE grading.14,28,29 Polte et al.30 found, with CMR, AR volume > 40 ml, and with TTE, AR fraction > 30% to be the best discriminator between patients with severe AR qualifying for guideline-recommended surgery,1 and patients with moderate AR. In our study LVEFTTE was significantly higher than LVEFCMR. Conversely, on CMR, LV volumes (LVEDVCMR and LVESVCMR) were significantly higher than LV volumes (LVEDVTTE and LVESVTTE) on TTE. CMR also allows an additional approach to the assessment of LV dilatation, which is not always consistent with TTE (Table 5). Underestimation of LV volumes by TTE is attributable to three factors: unreliable assessment of the LV apex, contouring of the inner edge of the LV trabeculations as endocardial borders, and use of geometric formulae for LVEF by TTE. Variability in echocardiographic measurement and underestimation of LV volumes may have important clinical implications if TTE results in underestimation of regurgitant severity or fails to recognise early LV remodelling in patients with chronic regurgitation.21 This could be resolved through the use of three-dimensional (3D) TTE. In our study, LVEDDTTE was correlated with RVolCMR. Our results showed that LVEDDTTE can be used, in accordance with contemporary guidelines, as a criterion for theoretical operability for LV remodelling. Contemporary guidelines recommend (class IIa; level B) surgery in asymptomatic patients with LVEDD > 70 mm and LVESD > 50 mm, based on TTE data.31 Concerning the clinical impact, five patients (10%) with inconclusive AR by TTE and severe AR by CMR had aortic valvular replacements. These results are important and show that AR quantification should be performed very carefully, and although it is performed by experienced TTE operators, it remains difficult and sometimes inaccurate. AR severity using TTE should be confirmed by CMR for reliable quantification and efficient therapeutic decision making. The main limitation of this study was its retrospective approach, which considerably limited TTE inter- and intraobserver variability analysis. The sample of patients who underwent CMR was relatively small. Moreover, even if the time delay between carrying out TTE and CMR was relatively short compared to the ongoing AR, some changes could have occurred, both in AR grade and in RV remodelling, between the two examinations. A prospective, multicentre study with current methods of quantification in 3D TTE and CMR, such as holodiastolic retrograde flow in the descending aorta, should be performed in order to assess AR accurately and to overcome significant interobserver variability.19,27 Conclusion CMR remains, in clinical practice, an insufficiently performed investigation for AR quantification. In our study, one in four patients underwent it over a decade. The re-grading of a number of severe AR cases on TTE into moderate AR on CMR is not insignificant and should motivate practitioners to systematically assess all severe AR on TTE with CMR in order to improve quantification and to proceed to an optimal clinical management. References 1. Joint Task Force on the Management of Valvular Heart Disease of the European Society of Cardiology (ESC); European Association for Cardio-Thoracic Surgery (EACTS), Vahanian A, Alfieri O, Andreotti F, Antunes MJ, Barón-Esquivias G, Baumgartner H, et al. Guidelines on the management of valvular heart disease (version 2012). Eur Heart J 2012; 33(19): 2451–2496. 2. Nishimura RA, Otto CM, Bonow RO, Carabello BA, Erwin JP, Guyton RA, et al. 2014 AHA/ACC guideline for the management of patients with valvular heart disease: executive summary: a report of the American College of Cardiology/American Heart Association task force on practice guidelines. Circulation 2014; 129: 2440–2492. 3. Lancellotti P, Tribouilloy C, Hagendorff A, Moura L, Popescu BA, Agricola E, et al; European Association of Echocardiography. European Association of Echocardiography recommendations for the assessment of valvular regurgitation. Part 1: Aortic and pulmonary regurgitation (native valve disease). Eur J Echocardiogr 2010; 11(3): 223–244. 4. Zoghbi WA, Enriquez-Sarano M, Foster E, Grayburn PA, Kraft CD, Levine RA, et al; American Society of Echocardiography. Recommendations for evaluation of the severity of native valvular regurgitation with two-dimensional and Doppler echocardiography. J Am Soc Echocardiogr 2003; 16(7): 777–802. 5. Lancellotti P, Moura L, Pierard LA, Agricola E, Popescu BA, Tribouilloy C, et al; European Association of Echocardiography. European Association of Echocardiography recommendations for the assessment of valvular regurgitation. Part 2: Mitral and tricuspid regurgitation (native valve disease). Eur J Echocardiogr 2010; 11(4): 307–332.
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